Condensing boiler and water heater

ABSTRACT

A boiler and method of operating a boiler are disclosed. The boiler generally includes a housing defining an enclosed region and a plurality of heat exchange conduits at least partially positioned within the enclosed region of the housing and arranged into an interior column and an exterior column. A baffle is at least partially positioned within the enclosed region of the housing and positioned between the interior column and the exterior column of heat exchange conduits. The baffle and the housing together define a constricted region. The heat exchange conduits of the exterior column are positioned within the constricted region. The constricted region defines a path for directing the flow of products of combustion adjacent the heat exchange conduits of the exterior column thereby facilitating the exchange of heat between the products of combustion and water within the heat exchange conduit of the exterior column.

FIELD OF THE INVENTION

The present invention relates to a hydronic boiler or water heater and a method of operating the same.

BACKGROUND OF THE INVENTION

Hydronic boilers operate by way of heating water (or any other fluid) to a preset temperature and circulating the water throughout a building or a home typically by way of radiators, baseboard heaters, and so forth. Hydronic boilers typically include a burner for introducing hot combustion gases into a housing of the boiler, and a heat exchanger including hollow tube members fitted within the boiler housing. Water is circulated through the hollow tube members of the heat exchanger for heat exchange with the hot combustion gases introduced into the boiler housing.

Hydronic boilers may also be referred to as condensing boilers when they are configured to condense the water vapor in the combustion gases to capture the latent heat of vaporization of the water produced during the combustion process. When water vapor condenses to a liquid phase onto a surface of the tube members, latent energy is released as sensible heat onto the surface of the tube members.

There is a need to further refine boilers to improve at least one of their performance, efficiency, cost and reliability. Furthermore, there is a need for such a boiler which also provides for easy cleaning of the interior of the hollow tube members of the heat exchanger.

SUMMARY OF THE INVENTION

In one exemplary aspect, a boiler is provided. The boiler comprises a housing defining an enclosed region and a plurality of heat exchange conduits at least partially positioned within the enclosed region of the housing. Each heat exchange conduit has a first end spaced apart from a second end thereof and a water passageway defined between the first end and the second end. The plurality of heat exchange conduits are arranged into an interior column and an exterior column, wherein each column includes at least one heat exchange conduit. A burner is positioned to deliver products of combustion into the enclosed region of the housing for heat exchange with water contained within the plurality of heat exchange conduits. A baffle is at least partially positioned within the enclosed region of the housing and positioned between the interior column and the exterior column of the heat exchange conduits. The baffle and the housing together define a constricted region and the at least one heat exchange conduit of the exterior column is positioned within the constricted region. The constricted region being configured to direct the flow of products of combustion adjacent the at least one heat exchange conduit of the exterior column thereby facilitating the exchange of heat between the products of combustion and water within the at least one heat exchange conduit of the exterior column.

In another exemplary aspect, an inlet conduit coupled to introduce water into the first end of the at least one heat exchange conduit of the exterior column. An outlet conduit is positioned to deliver water from either the first end or the second end of the at least one heat exchange conduit of the interior column. A bypass conduit is coupled to direct at least a portion of the water from the inlet conduit into either the first end or the second end of the at least one heat exchange conduit of the interior column or the exterior column, wherein the inlet conduit, outlet conduit and the bypass conduit are positioned at least partially outside of the enclosed region.

In yet another exemplary aspect, a method of operating a boiler is provided. The method comprises the step of introducing water into a first conduit of a heat exchanger of a boiler. Water is transferred from the first conduit to a second conduit of the heat exchanger, wherein the exterior surfaces of the first conduit and the second conduit are physically separated by a baffle. Products of combustion are delivered into an enclosed region of the boiler housing for heat exchange with water contained within the second conduit. The products of combustion are directed into a constricted region of the boiler housing defined between the baffle and the boiler housing for heat exchange with water contained within the first conduit.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is best understood from the following detailed description when read in connection with the accompanying drawings. It is emphasized that, according to common practice, the various features of the drawings are not to scale. On the On the contrary, the dimensions of the various features are arbitrarily expanded or reduced for clarity. Included in the drawings are the following figures:

FIG. 1 is a perspective view of an embodiment of a boiler including a heat exchanger.

FIG. 2 is a perspective view of the heat exchanger of the boiler of FIG. 1, wherein headers of the heat exchanger are shown exploded to reveal the exposed ends of the heat exchange conduits of the heat exchanger.

FIG. 3 is an exploded view of the heat exchanger of FIG. 2.

FIG. 4 depicts a top plan view of the heat exchanger of FIG. 2.

FIG. 5 is a front elevation view of the heat exchanger of FIG. 2 with the front surface of the headers removed to reveal the water flow paths.

FIG. 6 is a cross-sectional view of the boiler of FIG. 2 taken along the lines 6-6.

FIG. 7 is an exploded view of another exemplary embodiment of a heat exchanger of a boiler.

FIG. 8 is a cross-sectional perspective view of the heat exchanger of FIG. 7.

FIG. 9 is a front elevation view of the heat exchanger of FIG. 7 with the front surface of the headers removed to reveal the water flow paths.

DETAILED DESCRIPTION OF THE INVENTION

Although the invention is illustrated and described herein with reference to specific embodiments, the invention is not intended to be limited to the details shown. Rather, various modifications may be made to the illustrated embodiments within the scope and range of equivalents of the claims and without departing from the invention. Also, the embodiments selected for illustration in the figures are not shown to scale and are not limited to the proportions shown.

Referring generally to the figures and according to one exemplary aspect of the invention, a boiler 10 is provided. The boiler 10 comprises a housing 12 defining an enclosed region and a plurality of heat exchange conduits 30, 130 and 32, 132 at least partially positioned within the enclosed region of the housing 12. Each heat exchange conduit 30, 130 and 32, 132 has a first end 30 a and 32 a, respectively, spaced apart from a second end 30 b and 32 b, respectively, thereof and a water passageway defined between the first end 30 a and 32 a and the second end 30 b and 32 b. The plurality of heat exchange conduits 30, 130 and 32, 132 are arranged into an interior column C1 and an exterior column C2, wherein each column includes at least one heat exchange conduit. A burner 20 is positioned to deliver products of combustion into the enclosed region of the housing 12 for heat exchange with water contained within the plurality of heat exchange conduits 30, 130 and 32, 132. A baffle 31, 131 is at least partially positioned within the enclosed region of the housing 12 and positioned between the interior column C1 and the exterior column C2 of the heat exchange conduits 30, 130 and 32, 132. The baffle 31, 131 and the housing 12 together define a constricted region ‘C’ and the at least one heat exchange conduit 32, 132 of the exterior column C2 is positioned within the constricted region ‘C.’ The constricted region ‘C.’ The constricted region ‘C’ defines a path for directing the flow of products of combustion adjacent the at least one heat exchange conduit 32, 132 of the exterior column C2 thereby facilitating the exchange of heat between the products of combustion and water within the at least one heat exchange conduit 32 of the exterior column C2.

In another exemplary aspect, an inlet conduit 16 is configured to introduce water into the first end of the at least one heat exchange conduit 32, 132 of the exterior column C2. An outlet conduit 18 is positioned to deliver water from either the first end 30 a or the second end 30 b of the at least one heat exchange conduit 30, 130 of the interior column C1. A bypass conduit 26 is coupled to direct at least a portion of the water from the inlet conduit 16 into either the first end 30 a, 32 a or the second end 30 b, 32 b of the at least one heat exchange conduit 30, 130 or 32, 132 of the interior column C1 or the exterior column C2, wherein the inlet conduit 16, outlet conduit 18 and the bypass conduit 26 are positioned at least partially outside of the enclosed region of the housing 12.

In yet another exemplary aspect, a method of operating a boiler 10 is provided. The method comprises the step of introducing water into a first conduit 32, 132 of a heat exchanger 14, 114 of a boiler 10. Water is transferred from the first conduit 32, 132 to a second conduit 30, 130 of the heat exchanger 14, 114, wherein the exterior surfaces of the first conduit 32, 132 and the second conduit 30, 130 are physically separated by a baffle 31, 131. Products of combustion are delivered into an enclosed region of the boiler housing 12 for heat exchange with water contained within the second conduit 30, 130. The products of combustion are directed into a constricted region ‘C’ of the boiler housing 12 defined between the baffle 31, 131 and baffle 31, 131 and the boiler housing 12 for heat exchange with water contained within the first conduit 32, 132.

Referring now to FIG. 1, an exemplary embodiment of a boiler is designated by the numeral “10.” The boiler 10 generally includes a housing 12, a heat exchanger 14 (not entirely shown) contained within the housing 12, an inlet conduit 16 for delivering water (or other suitable liquid) into the heat exchanger, and an outlet conduit 18 for removing water (or other suitable liquid) from the heat exchanger 14.

The housing 12 of the boiler 10 generally includes a top cover 17, three walls 19 (right side wall shown; left side wall and rear wall not shown), a front panel 36, and a lower panel 57 (see FIG. 6) for encapsulating the heat exchanger 14. The walls of the housing 12 define an interior region of the housing 12. The heat exchanger 14 includes a series of conduits (not shown in FIG. 1) containing water (or any other suitable liquid) and a fuel-fired burner 20 for introducing products of combustion into the interior of the housing 12. Details of an exemplary burner 20 are described in U.S. Pat. No. 6,644,393, which is incorporated by reference herein in its entirety. The top cover 17, three walls 19, the front panel 36, and the lower panel 57 enclose the sides of the boiler housing 12 to limit or prevent products of combustion from inadvertently escaping.

In use, a supply of unheated or heated water (or any other suitable liquid) is delivered into the boiler 10 through the inlet conduit 16. The inlet conduit 16 includes an outlet port 24 for delivering water into one side of the heat exchanger 14. A bypass conduit 26 is fluidly coupled to a bypass port 22 of the inlet conduit 16. The bypass conduit 26 is configured to deliver water into the opposite side of the heat heat exchanger 14. Optionally, the bypass conduit 26 can be configured to deliver water into an inner conduit on the same side of the heat exchanger 14.

A valve 28 is mounted to the bypass conduit 26 for selectively permitting water to flow through the bypass conduit 26. In the open position of the valve 28, water is permitted to flow through the bypass conduit 26, and in a closed position of the valve 28, water is restricted from flowing through the bypass conduit 26. The purpose of the valve 28 and the bypass conduit 26 will be described in greater detail with respect to FIG. 5. Valve 28 is optionally a conventional shut-off valve. Alternatively, valve 28 can be a restricted orifice, a pressure regulating valve, or any other adjustable restriction.

FIGS. 2 and 3 depict a perspective and an exploded view, respectively, of the heat exchanger 14 of FIG. 1. The heat exchanger 14 generally includes a plurality of heat exchange conduits 30 and 32 for carrying water (or other suitable liquid), a baffle 31 positioned between the conduits 30 and 32 defining a flow path for products of combustion, a front panel 36, two header mounting plates 42 and 44 mounted to the front panel 36, and two headers 48 and 50 mounted to the header mounting plates 42 and 44, respectively.

The heat exchanger 14 may be referred to as a “two-pass” heat exchanger. More particularly, at least a portion of the water delivered through the inlet conduit 16 makes a first pass through the secondary heat exchange conduits 32 and is preheated by the products of combustion passing over the secondary heat exchange conduits 32. By way of example, about 20% to about 25% of the thermal energy of the products of combustion is transferred to the water within the secondary heat exchange conduits 32. The preheated water then makes a second pass through the primary heat exchange conduits 30 and is heated by the products of combustion passing over the primary heat exchange conduits 30. By way of example, about 75% to about 80% of the thermal energy of the products of combustion is transferred to the water within the heat exchange conduits 30.

The heat exchanger includes ten primary heat exchange conduits 30(1) through 30(10) (referred to collectively as conduits 30) and ten secondary heat exchange conduits 32(1) through 32(10) (referred to collectively as conduits 32). Alternatively, the heat exchanger includes eight primary heat exchange conduits and eight secondary heat exchange conduits. Additionally, smaller and larger numbers of conduits are contemplated as well, depending on the size or capacity of the system. Also, the number of primary and secondary conduits can be the same (as illustrated) or their numbers may be different. For example, there may be a larger number of primary or secondary conduits as compared to secondary and primary conduits, respectively.

Each conduit 30 and 32 includes a first end portion 30 a and 32 a, respectively, spaced apart from a second end portion 30 b and 32 b, respectively. A hollow liquid passageway having a circular cross-section is defined between the first end portion 30 a and 32 a and the second end portion 30 b and 32 b of each conduit 30 and 32, respectively. The cross-sectional shape of the liquid passageway may vary without departing from the scope or spirit of the invention. Although not shown, each conduit 30 and 32 may include heat sink fins extending from or forming part of its exterior surface (see FIG. 8, for example). The heat sink fins increase the heat transfer between the liquid distributed through the liquid passageway and the products of combustion delivered into the housing 12 by the burner 20.

The conduits 30 and 32 are arranged into two vertical columns C1 and C2. In assembled form, the exterior column C2 of conduits 32 surrounds or extends about the interior column C1 of conduits 30. According to the exemplary embodiment illustrated herein, each column C1 and C2 includes ten conduits 30 and 32, respectively. The heat exchanger 14 may include any number of conduits 30 and 32, and is thereby not limited to a specific number of conduits 30 and 32. The conduits 30 and 32 of each column C1 and C2, respectively, may optionally be fastened together by a weld, clamp, bracket, mechanical fastener, strap, or any other fastening means known to those skilled in the art.

The baffle 31 is positioned to extend between the columns C1 and C2 of conduits 30 and 32, respectively. The column C1 of conduits 30 are positioned within the baffle 31, whereas the column C2 of conduits 32 are positioned outside of the baffle 31. In this exemplary embodiment, the baffle 31 includes a single “U” shaped wall 40 positioned to extend between the columns C1 and C2 of “U” shaped conduits 30 and 32, respectively. As will be described with reference to FIG. 6, the wall 40 of the baffle is configured to direct the products of combustion through the heat exchanger 14 along a pre-determined path.

The baffle 31 includes a floor surface 49 for limiting or preventing inadvertent escape of combustion products through the lower end of the heat exchanger 14. Opposite the floor surface 49, the top end of the baffle 31 is exposed for inducing the flow of combustion products over the wall 40 of the baffle 31 as described in greater detail with reference to FIG. 6. Although not shown, the floor surface 49 of the baffle 31 or other surface of the housing may include a condensate outlet port, or other provisions, to facilitate the draining of condensation formed on the interior surfaces of of the baffle 31 and the exterior surfaces of the conduits 30. A drain, tube or pipe (not shown) may be coupled to the condensate outlet port for removing the condensate from the boiler 10.

The front panel 36 is mounted to the baffle 31 by a swaging operation. Alternatively, the front panel 36 may be mounted to the baffle 31 by a series of fasteners (not shown). An aperture 43 is defined in the center of the front panel 36 for accommodating the burner 20 (see FIG. 1). Although not shown, the circular aperture 43 may have a square shape or any other shape for accommodating the burner 20, depending on the shape or size of the burner selected for use in the boiler 10. The burner 20 is configured to introduce products of combustion into the interior region of the boiler housing 12. A mounting flange 45, which surrounds the aperture 43, is provided for mounting the burner 20 to the front panel 36. A series of holes (not shown), studs or fasteners may be positioned or defined on the mounting flange 45 for mounting the burner 20 onto the front panel 36.

Two header mounting plates 42 and 44 are mounted to the front panel 36 by a series of fasteners. Two headers 48 and 50 are mounted to the header mounting plates 42 and 44, respectively, by a series of fasteners (not shown) or any other means for fastening known to those skilled in the art. The headers 48 and 50 conceal the exposed ends of the conduits 30 and 32. Although not shown, a compressible, elastomeric gasket may be positioned at the interface between each header 48 and 50 and its respective header mounting plate 42 and 44, respectively, for limiting leakage of water.

The first header 48 includes a inlet opening 52 for coupling with the outlet port 24 of the inlet conduit 16. The second header 50 includes a secondary inlet opening 54 for coupling with the an outlet port 27 of the bypass conduit 26. The second header 50 further includes an outlet opening 56 for coupling with the outlet conduit 18 and providing a passageway for removing heated water from the conduits 30 and 32 of the heat exchanger 14.

In assembled form, the conduits 30 are coupled (either directly or indirectly) to the front plate 36 of the housing 12 and both header mounting plates 42 and 44. According to one exemplary method of assembling heat exchanger 14, the first end portion 30 a of each conduit 30 is sequentially positioned through a respective aperture 34(III) defined on a flange of the front plate 36 and a respective aperture 38(III) defined on the header mounting plate 42. Similarly, the second end portion 30 b of each conduit 30 is sequentially positioned through a respective aperture 34(II) defined on the front plate 36 and a respective aperture 38(II) defined on the header mounting plate 44.

The conduits 32 are coupled (either directly or indirectly) to the baffle 31, the front plate 36, and both header mounting plates 42 and 44. More particularly, the first end portion 32 a of each conduit 32 is sequentially positioned through a respective aperture 39(II) defined on a flange of the baffle 31, a respective aperture 34(IV) defined on the front plate 36, and a respective aperture 38(IV) defined on the header mounting plate 42. Similarly, the second end portion 32 b of each conduit 32 is sequentially positioned through a respective aperture 39(I) defined on the flange of the baffle 31, a respective aperture 34(I) defined on the front plate 36, and a respective aperture 38(I) defined on the header mounting plate 44.

According to one aspect of the invention and as best shown in FIG. 3, the wall thickness of each conduit end portion 30 a, 30 b, 32 a and 32 b is optionally less than the wall thickness of the remaining segment of each conduit. A shoulder 30 c and 32 c is optionally formed at the interface between the thin-walled end portion and the remaining segment of the conduits 30 and 32, respectively. In assembly, the shoulder is positioned to abut the rear face (not shown) of the front plate 36. Alternatively, and as an alternative to shoulders 30 c and 32 c, fins attached to the conduit ends or end portions abut the rear face of the front plate 36. The end portions 30 a, 30 b, 32 a and 32 b of the conduits 30 and 32 are each positioned to extend through the front panel 36 of the heat exchanger. The end portions 30 a and 32 a of the conduits 30 and 32, respectively, are thereafter swaged over the header mounting plate 42. Similarly, the end portions 30 b and 32 b of the conduits 30 and 32, respectively, are swaged over the header mounting plate 44.

Swaging the end portions 30 a, 30 b, 32 a and 32 b, as shown, captivates the conduits 30 and 32 to the baffle 31, the front plate 36, and both header mounting plates 42 and 44. Additionally, the end portions 30 a, 30 b, 32 a and 32 b of the conduits are swaged for accomplishing a liquid-tight seal between the header mounting plate 42 and 44 and the swaged end portions 30 a, 30 b, 32 a and 32 b. As shown in FIG. 2, to enhance the sealing properties at that interface, a gasket 55 is optionally positioned between the front surface of the header mounting plate 42 or 44 and each swaged conduit end portion. The gasket 55 may take the form of an elastomeric o-ring as shown or any other sealing means known to those skilled in the art.

A lower refractory panel 47 is positioned between the bottom conduit 30(10) and the floor 49 of the baffle 31. Similarly, a top support panel 51 is positioned between the top conduit 30(1) and the top cover 17 of the housing 12. The upper support panel 51 and the lower refractory panel 47, respectively, are optionally mounted to the conduits by a series of straps 53 (two shown) for added structural support. It should be understood that a variety of ways exist for mounting the upper and lower panels 51 and 47 to the conduits 30.

FIG. 4 depicts a top plan view of the heat exchanger 14 of FIG. 1. The overall shape of each conduit 30 and 32 is substantially “U”-shaped. It should be understood that the geometry of the conduits 30 and 32 may differ from the “U”-shape illustrated herein without departing from the scope and spirit of the invention. The plurality of conduits 30 and 32 are arranged side-by-side into an interior column C1 and an exterior column C2, respectively. The columns C1 and C2 are optionally stacked coaxially, i.e., the arcuate portion of the conduits 30 of column C1 optionally share the same axis “A” with the arcuate portion of the conduits 32 of column C2. Aligning the axes “A” of columns C1 and C2 maintains a substantially constant horizontal spacing “S” between the columns C1 and C2 of conduits 30 and 32, respectively, to accommodate the baffle 31 between the columns C1 and C2.

The exterior column C2 of conduits 32 is positioned outwardly from the interior column C1 of conduits 30. It follows that the horizontal distance between the first end portion 32 a and the second end portion 32 b of each conduit 32 is greater than the horizontal distance between the first end portion 30 a and the second end portion 30 b of each conduit 30. The baffle 31 is positioned between the columns C1 and C2 of conduits 30 and 32, respectively. The baffle 31 is substantially “U”-shaped for for mounting between the “U”-shaped columns C1 and C2. It should be understood that the shape of the baffle 31 may depart from that shown to conform to the shape of the conduits 30 and 32.

FIG. 5 depicts a front elevation view of the heat exchanger 14 of FIG. 2 illustrating the front surfaces of the headers 48 and 50, respectively, in phantom to reveal the exposed ends of the conduits 30 and 32. The headers 48 and 50 are configured to direct the water into and out of the heat exchanger 14, as well as to direct water through the individual conduits 30 and 32 of the heat exchanger 14. The headers 48 and 50 include a series of interior partitions 60 and 62, respectively, for isolating the water flow into respective channels Z1 through Z8. The channels Z1 through Z8 are defined by the partitions 60 and 62 of the headers 48 and 50, respectively. The partitions 60 of the header 48 delineate four channels within the header 48, i.e., channels Z1, Z3, Z5 and Z7. The partitions 62 of the header 50 delineate four channels within the header 50, i.e., channels Z2, Z4, Z6 and Z8.

The partitions 60 and 62 are positioned to retain water in a respective channel. Each partition 60 and 62 is a solid wall that extends the entire width “W” of the header 48 and 50 (see FIG. 2), respectively. Although not shown, an elastomeric gasket may be positioned at the interface between each partition 60 and 62 and the header mounting plate 42 and 44. The elastomeric gasket is provided to maintain the water within a particular channel and to limit the water from inadvertently entering an adjacent channel.

The purpose of the headers 48 and 50, the partitions 60 and 62 and the channels Z1 through Z8 are best described with reference to the operation of the heat exchanger 14. According to one exemplary use of this invention, water is first introduced into the inlet conduit 16 (see FIG. 1). A portion of the water flows through the outlet port 24 of the inlet conduit 16, through the inlet opening 52 of the first header 48, and into channel Z1.

Upon entering the channel Z1, the water fills the channel Z1 and flows into the first end of conduits 32(1) and 32(2). In FIG. 5, the exposed ends of every conduit 30 and 32 includes a symbol designating water flow. The symbol ‘*’ denotes that water is entering the end of a conduit, whereas the symbol ‘•’ denotes that water is exiting from the end of a conduit. The water travels through conduits 32(1) and 32(2) and exits into channel Z2 of the second header 50. The water then fills the channel Z2 and flows into the second end of conduits 32(3) and 32(4). The water travels through conduits 32(3) and 32(4) and exits into channel Z3 of the first header 48. The water fills the channel Z3 and flows into the first end of conduits 32(5) and 32(6). The water travels through conduits 32(5) and 32(6) and exits into channel Z4 of the second header 50. The water fills the channel Z4 and flows into the second end of conduits 32(7) and 32(8). The water travels through conduits 32(7) and 32(8) and exits into channel Z5 of the first header 48. The water fills the channel Z5 and flows into the first end of conduits 32(9) and 32(10). The water travels through conduits 32(9) and 32(10) and exits into channel Z6 of the second header 50.

Water is also introduced into the channel Z6 through the bypass opening 54 of the second header 50. By way of non-limiting example, about approximately 20% of the water introduced into the heat exchanger 14 flows into the inlet opening 52 of the first header 48, and the remaining portion of the water flows into the bypass opening 54 of the second header 50. A lower proportion of the water is introduced through through the inlet opening 52 in an effort to reduce the pressure drop through the exterior column of conduits 32. The relative proportions of water flow, however, may be altered through adjustment of the valve 28 provided on the bypass conduit 26.

Both sources of water, either alone or in combination, fill the channel Z6 and flow into the second end of conduits 30(6), 30(7), 30(8), 30(9) and 30(10). The water then travels through conduits 30(6), 30(7), 30(8), 30(9) and 30(10) and exits into channel Z7 of the first header 48. The water fills the channel Z7 and flows into the first end of conduits 30(1), 30(2), 30(3), 30(4) and 30(5). The channel Z7 includes the first ends of the entire interior column C1 of conduits 30. The water then travels through conduits 30(1), 30(2), 30(3), 30(4) and 30(5) and exits into channel Z8 of the second header 50. The water fills the channel Z8 of the second header 50 and flows into the outlet opening 56 provided in the second header 50. The water is ultimately carried away by the outlet conduit 18 that is coupled to the outlet opening 56 of the second header 50.

Those skilled in the art will recognize that various ways exist to direct the flow of water through the conduits 30 and 32 without departing from the scope or spirit of the invention, and the invention is not limited to any particular flow path.

FIG. 6 is a cross-sectional view of the boiler of FIG. 1 taken along the lines 6-6. As best shown in FIG. 6, the heat exchanger 14 of FIGS. 2-4 is positioned between the top panel 17 and the lower panel 57 of the boiler housing 12. A partition 72 extends between the top panel 17 and the lower panel 57 of the boiler housing 12 and is positioned outwardly from the outer column of conduits 32. The partition 72 is a “U” shaped wall having substantially the same radius of curvature as the wall 40 of the baffle 31. A gap “C” of substantially constant width is defined radially between the baffle wall 40 and the partition 72. The gap “C” is referred to hereinafter as constricted region “C”, the significance of which will be explained in greater detail later. According to this exemplary embodiment, the partition 72 is a component of the boiler housing 12. Alternatively, the partition 72 may be a component of the heat exchanger 14. As another alternative, the side walls 19 (see FIG. 1) of the boiler housing 12 may form the partition.

The flow of combustion products along a defined flow passageway is depicted by a series of arrows labeled ‘1’ through ‘6’ in FIG. 6. Products of combustion are first introduced into the interior region of the boiler housing 12 by the burner 20 (not shown in this figure). The products of combustion initially expand to fill the interior portion 70 of the housing that is circumscribed by the interior column of conduits 30, as indicated by the eight horizontal arrows labeled ‘1.’ Heat from the products of combustion is transferred to the water within the conduits 30 through convective and radiant heat transfer. By way of example, about 75% to about 80% of the thermal energy of the products of combustion is transferred to the water within the conduits 30.

The products of combustion are then induced to flow between gaps (not shown) provided between the exterior surfaces of adjacent conduits 30. These gaps are optionally defined by fins formed on the conduits 30. The gaps may also be provided by spaces defined between the conduits 30. The products of combustion are then urged or forced to flow in an upward direction and along the opposite surface of the conduits 30 as indicated by the vertical arrows labeled ‘2.’ The products of combustion are then induced to flow through the gap “G” provided between the top cover 17 of the housing 12 and the top edge of the wall 40 of the baffle 31, as baffle 31, as indicated by the horizontal arrows labeled ‘3.’

The products of combustion are then induced to flow through the constricted region “C” defined between the baffle wall 40 and the partition 72 of the boiler housing 12, as indicated by the vertical arrows labeled ‘4.’ The conduits 32 are positioned within the constricted region “C.” Heat from the products of combustion is transferred to the water within the conduits 32 through convective heat transfer. By way of example, about 20% to about 25% of the thermal energy of the products of combustion is transferred to the water within the conduits 32. The purpose of the constricted region “C” will be described in greater detail later.

After passing through the constricted region “C,” the products of combustion collect in an exhaust chamber 74 positioned beneath the heat exchanger 14, as indicated by the horizontal arrows labeled ‘5.’ The exhaust chamber 74 is bounded by the lower panel 57 of the boiler housing 12, the lower portion of the partition 72 and the floor 49 of the baffle 31. The products of combustion are then drawn through an exhaust opening 76 provided in the lower panel 57 of the boiler housing 12, as indicated by the vertical arrow labeled ‘6.’ The exhaust opening 76 is positioned proximal to and in flow communication with the constricted region “C.” Although not shown, an exhaust conduit may be coupled to the exhaust opening 76 for removing the products of combustion from the boiler 10.

As indicated previously, the products of combustion are induced to flow through the constricted region “C” defined between the baffle wall 40 and the partition 72 of the boiler housing 12, as indicated by the vertical arrows labeled ‘4.’ Both the total volume and cross-sectional area of the constricted region “C” is significantly less than the total volume and cross-sectional area of the interior portion 70 of the housing 12 circumscribed by the interior column of conduits 30, as depicted by the cross-sectional view of FIG. 6. According to one embodiment of the invention the total cross-sectional area of the constricted region “C” is about 152 square-inches, for example. In contrast, the total cross-sectional area of the interior portion 70 of the housing 12 is about 849 square-inches, for example.

Upon entering the constricted region “C,” the velocity of the combustion products substantially increases as a result of the reduced cross-sectional area of the constricted region “C.” By way of example, the velocity of the products of combustion in the interior portion 70 of the housing 12 is about 1.1 feet/second and the velocity of the products of combustion in the constricted region “C” is about 6.4 feet/second. The high-velocity products of combustion within the constricted region “C” results in a greater heat exchange between the products of combustion and the water within the exterior column of conduits 32. By way of example, about 20% to about 25% of the thermal energy of the products of combustion is transferred to the water within the conduits 32.

The products of combustion flowing through the constricted region “C” release sufficient heat to cause the water vapor in the products of combustion to condense on the outer surfaces of the conduits 32. As background, condensate is introduced through combustion as a byproduct of the combustion reaction, and hot combustion gases therefore contain relatively large quantities of moisture. When the hot combustion gas is cooled, the temperature of the gas drops. As this occurs, the amount of moisture that the gas can hold decreases and at some distance from the combustion source, the water condenses on any surface that is below the dew point of the gas mixture. The dew point is the temperature to which a given parcel of air must be cooled, at constant barometric pressure, for water vapor to condense into water. Hydronic boilers are tailored to condense the water vapor in the combustion gases to capture the latent heat of vaporization of the water produced during the combustion process. When the water vapor condenses to a liquid phase onto a surface of the conduits 32, latent energy is released as sensible heat onto the surface of the conduits 32, thereby transferring heat to the water within the conduits 32.

Condensate is typically acidic, with pH values often in the range of between about 2 to 5. The formation of increased amounts of such acidic condensate, even in relatively small quantities, can accelerate the corrosion of heat exchange tubing, increase oxidation and scale formation, reduce heat exchange efficiency and contribute to failure of the boiler. To limit or prevent corrosion in the presence of water, the conduits 30 and 32 are optionally formed from stainless steel, aluminum or coated copper; the header mounting plates 42 and 44 are optionally composed of carbon steel; and the front panel 36 is optionally composed of stainless steel. The headers 48 and 50 are optionally composed of carbon steel. The interior of the headers 48 and 50 and the conduits 30 and 32, or any other component of the boiler 10 in the presence of water, may be lined with glass for safely distributing potable water. It should be understood by those skilled in the art that the individual components of the boiler 10 may be formed from a variety of materials without departing from the spirit or scope of the invention.

The heat exchanger 14 confers several benefits over conventional heat exchangers. First, the heat exchanger 14 can withstand a greater quantity of condensate without exhibiting corrosion because the conduits 30 and 32 are formed from a material that resists corrosion in the presence of water. Accordingly, because introducing lower inlet water temperatures into a heat exchanger results in greater quantities of condensate and the conduits 30 and 32 are formed from a corrosion resistant material, water may be introduced into the heat exchanger 14 at a lower temperature. For example, water may be introduced into the heat exchanger 14 at 40° F., as compared with conventional boilers which are designed to receive water pre-heated or heated to a temperature of at least 130° F. Because the heat exchanger 14 can efficiently process low-temperature water, the incoming water does not have to be pre-heated, thereby resulting in a significant energy savings.

Second, increasing the velocity of the combustion products passing over the conduits 32 maximizes the heat exchange therebetween, thereby resulting in a better utilization of the heat exchange material as compared with heat exchangers of conventional boilers. Accordingly, less heat exchange material (i.e., fewer or smaller conduits 32) is required to achieve the same level of heat exchange efficiency observed in conventional boilers, thereby resulting in a significant material cost savings.

Third, the heat exchanger 14 is configured for the efficient removal of condensate from the interior of the housing 12. Although not shown, the lower panel 57 and the floor surface 49 of the baffle 31 may include a condensate outlet port, or other provisions, to facilitate the draining of condensation formed on the interior surfaces of the heat exchanger 14. A drain, tube or pipe (not shown) may be coupled to the condensate outlet port for removing the condensate from the boiler 10. Furthermore, the high-velocity products of combustion flowing through the constricted region “C” urge the condensate formed on the conduits 32 in a direction towards the aforementioned condensate removal provisions provided in the lower panel 57.

Fourth, by virtue of the unique design of the heat exchanger 14, the boiler can be configured to operate at about 93% efficiency to about 97% efficiency, as compared with traditional hydronic boilers which operate at 90% efficiency. One measurement of the efficiency of a boiler is the annual fuel utilization efficiency (AFUE). AFUE is the ratio of heat output of the boiler compared to the total energy consumed by a boiler. An AFUE of 90%, for example, indicates that 90% of the energy in the fuel becomes heat for the installation and the other 10% escapes through outlet piping.

Referring back to FIG. 5, many of the serviceable components of the heat exchanger 14 are conveniently located on the front panel 36 of the heat exchanger 14. The headers 48 and 50 are removable for line-of-sight access to the interior surfaces of the conduits 30 and 32 for cleaning and/or maintenance. Upon removal of the headers 48 and 50, the interior surfaces of the conduits 30 and 32, the headers 48 and 50, and the header mounting plates 42 and 44 may be cleaned and serviced. Additionally, the burner 20 is conveniently positioned on the front panel 36 of the heat exchanger 14 for removal and servicing.

By positioning the burner 20, the ends of the conduits 30 and 32, and the headers 48 and 50 on the front panel 36, multiple boilers 10 may be positioned side-by-side in an installation to save valuable floor space.

FIGS. 7-9 depict another exemplary embodiment of a heat exchanger 114 of a boiler. This embodiment is similar to the heat exchanger embodiment illustrated in FIG. 4 with various exceptions, as described hereinafter.

As best shown in FIG. 7, the heat exchanger 114 generally includes a plurality of heat exchange conduits 130 and 132 for carrying water (or other suitable liquid), a baffle 131 positioned between the conduits 130 and 132 defining a flow path for products of combustion, two header mounting plates 142 and 144 mounted to the front panel 136, and two headers 148 and 150 mounted to the header mounting plates 142 and 144, respectively.

Unlike the baffle 31 of FIG. 3, the baffle of FIG. 7 is divided into two separate components, i.e., baffle 131 and mounting plate 191. The mounting plate 191 includes apertures 139(1) and 139(2) for receiving the ends of the conduits 130, whereas the baffle 31 of FIG. 3 includes apertures 39(1) and 39(2) for receiving the ends of the conduits 30.

The heat exchanger 114 of FIGS. 7-9 includes an interior column C1 of eight conduits 130 and an exterior column C2 of eight conduits 132, as opposed to ten conduits. Accordingly, the water flow path through the heat exchanger 114 of FIG. 7 is different from the water flow path through the heat exchanger 14 of FIG. 3, as described in greater detail with respect to FIG. 9. Moreover, unlike the headers 48 and 50 of FIG. 3, the header 148 of FIG. 7 includes an inlet opening 152, a bypass opening 154, and an outlet opening 156.

Each conduit 130 and 132 includes heat-sink fins 197 longitudinally spaced along its entire length to maximize heat transfer between the products of combustion and the fluid within the conduits 130 and 132.

Unlike the heat exchanger of FIG. 4, the heat exchanger 114 includes a series of baffles 190 to maximize heat transfer between the products of combustion and the fluid within the conduits 130 and 132. As best shown in FIG. 8, baffles 190 are positioned on the exterior surface of conduits 130 between adjacent conduits 130. The baffles 190 optionally extend along the entire height and the entire exterior perimeter of the conduits 130.

Each baffle 190 includes a “U” or “V” shaped portion which is sized to fit between the revolved surface of adjacent conduits 130, as best shown in FIG. 8. One or more spring clips 192 are mounted to each baffle 190. In assembled form, the spring clips 192 are compressed between the conduits 130 and the wall of the baffle 131, such that the baffles 190 remain in place. Those skilled in the art will recognize that other ways exist to mount the baffles 190 to the conduits 130.

Adjacent baffles 190 are separated by a gap 194. In use, the products of combustion flow between the fins 197 of the conduits 130 and pass through the gaps 194 provided between the conduits 130. Inducing the products of combustion through the gaps 194 maximizes heat transfer between the products of combustion and the fluid within the conduits 130.

In addition to the baffles 190, a series of baffles 195 (fourteen shown) are positioned in every interior and exterior crevice defined between adjacent conduits 132, as shown in FIG. 7. According to one aspect of the invention, the baffles 195 are provided in the form of fiberglass rope. The baffles 195, however, may be composed of any material known to those skilled in the art.

In use, the products of combustion flow between the fins 197 of the conduits 132. The baffles 195 direct the products of combustion toward the flow passages of the conduits 132, thereby maximizing heat transfer between the products of combustion and the fluid within the conduits 132.

Referring now to FIG. 9, and according to one exemplary use of this invention, water is first introduced into an inlet opening 152 provided in the first header 148 and into channel X1. The symbol ‘*’ denotes that water is entering the end of a conduit, whereas the symbol ‘’ denotes that water is exiting from the end of a conduit. Upon entering the channel X1, the water fills the channel X1 and flows into the first end of conduits 132(1) and 132(2). The water travels through conduits 132(1) and 132(2) and exits into channel X2 of the second header 150. The water then fills the channel X2 and flows into the second end of conduits 132(3) and 132(4). The water travels through conduits 132(3) and 132(4) and exits into channel X3 of the first header 148. The water fills the channel X3 and flows into the first end of conduits 132(5) and 132(6). The water travels through conduits 132(5) and 132(6) and exits into channel X4 of the second header 150. The water fills the channel X4 and flows into the second end of conduits 132(7) and 132(8). The water travels through conduits 132(7) and 132(8) and exits into channel X5 of the first header 148.

Water is also introduced into the channel X5 through the bypass opening 154 of the second header 150. By way of non-limiting example, about approximately 20% of the water introduced into the heat exchanger 114 flows into the inlet opening 152 of the first header 148 and the remaining portion of the water flows into the bypass opening 154 of the second header 150. A lower proportion of the water is introduced through the inlet opening 152 in an effort to reduce the pressure drop through the exterior column of conduits 132. The relative proportions of water flow, however, may be altered through adjustment of a valve provided on the inlet conduit (not shown).

Both sources of water, either alone or in combination, fill the channel X5 and flow into the second end of conduits 130(5), 130(6), 130(7) and 130(8). The water then travels through conduits 130(5), 130(6), 130(7) and 130(8) and exits into channel X6 of the second header 150. The water fills the channel X6 and flows into the first end of conduits 130(1), 130(2), 130(3) and 130(4). The channel X6 includes the second ends of the entire interior column C1 of conduits 130. The water then travels through conduits 130(1), 130(2), 130(3) and 130(4) and exits into channel X7 of the first header 148. The water fills the channel X7 of the first header 148 and flows into the outlet opening 156 provided in the first header 148. The water is ultimately carried away by an outlet conduit (not shown) that is coupled to the outlet opening 156 of the first header 148. As noted previously, those skilled in the art will recognize that various ways exist to direct the flow of water through the conduits 130 and 132 without departing from the scope of spirit of the invention, and the invention is not limited to any particular flow path.

While preferred embodiments of the invention have been shown and described herein, it will be understood that such embodiments are provided by way of example only. Numerous variations, changes and substitutions will occur to those skilled in the art without departing from the spirit of the invention. Accordingly, it is intended that the appended claims cover all such variations as fall within the spirit and scope of the invention. 

1. A boiler comprising: a housing defining an enclosed region; a plurality of heat exchange conduits at least partially positioned within the enclosed region of the housing, each heat exchange conduit having a first end spaced apart from a second end thereof and a water passageway defined between said first end and said second end, said plurality of heat exchange conduits being arranged into an interior column and an exterior column, each column including at least one heat exchange conduit; a burner positioned to deliver products of combustion into the enclosed region of the housing for heat exchange with water contained within said plurality of heat exchange conduits; and a baffle at least partially positioned within said enclosed region of said housing and positioned between the interior column and the exterior column of said heat exchange conduits, said baffle and said housing together defining a constricted region and said at least one heat exchange conduit of said exterior column being positioned within said constricted region; said constricted region being configured to direct the flow of products of combustion adjacent said at least one heat exchange conduit of said exterior column thereby facilitating an exchange of heat between the products of combustion and water within said at least one heat exchange conduit of said exterior column.
 2. The boiler of claim 1, wherein a cross-sectional area of said constricted region is sized to increase the velocity of the products of combustion flowing therethrough.
 3. The boiler of claim 1, wherein each heat exchange conduit is substantially “U” shaped, and said first end and said second end of each heat exchange conduit are positioned to face in substantially the same direction.
 4. The boiler of claim 3, said first ends and said second ends of said plurality of heat exchange conduits being arranged on a common plane.
 5. The boiler of claim 1, wherein said at least one heat exchange conduit of said exterior column is positioned outwardly from said at least one heat exchange conduit of said interior column.
 6. The boiler of claim 1, said burner being positioned to deliver the products of combustion into a region circumscribed by the at least one heat exchange conduit of said interior column.
 7. The boiler of claim 1 further comprising an inlet conduit coupled to introduce water into said first end of said at least one heat exchange conduit of said exterior column.
 8. The boiler of claim 7 further comprising a bypass conduit coupled to direct at least a portion of water within said inlet conduit into said second end of said at least one heat exchange conduit of said interior column or the first end or the second end of said at least one heat exchange conduit of said exterior column.
 9. The boiler of claim 8, wherein said bypass conduit and said inlet conduit are positioned at least partially outside of said enclosed region of said housing.
 10. The boiler of claim 1 further comprising an outlet conduit being positioned to receive water from either the first end or the second end of said at least one heat exchange conduit of said interior column.
 11. The boiler of claim 1 further comprising an exhaust outlet positioned in flow communication with said constricted region for exhausting said products of combustion from said enclosed region of said housing.
 12. A boiler comprising: a housing defining an enclosed region; a plurality of heat exchange conduits at least partially positioned within said enclosed region, each heat exchange conduit having a first end spaced apart from a second end thereof and a water passageway defined between said first end and said second end, said plurality of heat exchange conduits being arranged into an interior column and an exterior column, each column including at least one heat exchange conduit; an inlet conduit coupled to introduce water into said first end of said at least one heat exchange conduit of said exterior column; an outlet conduit positioned to deliver water from either said first end or said second end of said at least one heat exchange conduit of said interior column; and a bypass conduit coupled to direct at least a portion of the water from said inlet conduit into either said first end or said second end of said at least one heat exchange conduit of said interior column or said exterior column, wherein said inlet conduit, said outlet conduit and said bypass conduit are positioned at least partially outside of said enclosed region of said housing.
 13. The boiler of claim 12 further comprising an adjustable restriction positioned on the bypass conduit for selectively directing at least a portion of the water from said inlet conduit into either said first end or said second end of said at least one heat exchange conduit of said interior column or said exterior column.
 14. The boiler of claim 12, wherein said interior column includes a plurality of heat exchange conduits and the exterior column includes a plurality of heat exchange conduits.
 15. The boiler of claim 14 further comprising a header communicating with said first ends of said interior column of heat exchange conduits and said first ends of said exterior column of said heat exchange conduits, wherein said inlet conduit is positioned to deliver water into said first header.
 16. The boiler of claim 15 further comprising a partition within said header positioned to isolate one or more of said first ends of said interior column of said heat exchange conduits from one or more of said first ends of said exterior column of said heat exchange conduits.
 17. The boiler of claim 15 wherein the header is configured to direct water from said first end of at least one heat exchange conduit of said interior column to the first end of at least one adjacent heat exchange conduit of said interior column.
 18. The boiler of claim 15 wherein the header is configured to direct water from the first end of at least one heat exchange conduit of said exterior column to the first end of at least one adjacent heat exchange conduit of said exterior column.
 19. The boiler of claim 14 further comprising a header communicating with said second ends of said interior column of said heat exchange conduits and said second ends of said exterior column of said heat exchange conduits, wherein said outlet conduit is positioned to receive water from said header, and wherein said bypass conduit is coupled to deliver water into said header.
 20. The boiler of claim 19 further comprising a partition within said header positioned to direct water from said second end of at least one heat exchange conduit of said exterior column into said second end of at least one heat exchange conduit of said interior column.
 21. The boiler of claim 19 wherein the header is configured to direct water from the second end of at least one heat exchange conduit of said interior column to the second end of at least one adjacent heat exchange conduit of said interior column.
 22. The boiler of claim 19 wherein the header is configured to direct water from the second end of at least one heat exchange conduit of said exterior column to the second end of at least one adjacent heat exchange conduit of said exterior column.
 23. The boiler of claim 13, said adjustable restriction comprising a valve.
 24. A method of operating a boiler including a heat exchanger positioned at least partially within an enclosed region of a boiler housing, said method comprising the steps of: introducing water into a first conduit of the heat exchanger; transferring water from the first conduit to a second conduit of the heat exchanger, wherein exterior surfaces of the first conduit and the second conduit are physically separated by a baffle; delivering products of combustion into the enclosed region of the boiler housing for heat exchange with water contained within the second conduit; and directing the products of combustion into a constricted region of the boiler housing defined between the baffle and the boiler housing for heat exchange with water contained within the first conduit.
 25. The method of claim 24, wherein the introducing step comprises introducing water into the first conduit through an inlet conduit at least partially positioned outside of the boiler housing.
 26. The method of claim 25, wherein the introducing step further comprises directing at least a portion of the water from the inlet conduit into the second conduit.
 27. The method of claim 24 further comprising the step of exhausting the products of combustion through an exhaust outlet positioned in flow communication with the constricted region.
 28. A method of operating a boiler including a heat exchanger positioned at least partially within an enclosed region of a boiler housing, said method comprising the steps of: introducing water through an inlet conduit into an end of at least one heat exchange conduit in an exterior column of heat exchange conduits; delivering water through an outlet conduit from an end of at least one heat exchange conduit in an interior column of heat exchange conduits; and directing at least a portion of the water through a bypass conduit from the inlet conduit into an end of at least one heat exchange conduit in the interior or exterior column of heat exchange conduits.
 29. The method of claim 28 wherein the directing step comprises adjusting an adjustable restriction positioned on the bypass conduit to selectively direct at least a portion of the water through the bypass conduit.
 30. The method of claim 28 wherein the directing step comprises directing at least a portion of the water into a header that is positioned in fluid communication with the end of the at least one heat exchange conduit in the interior or exterior column of heat exchange conduits.
 31. The method of claim 30 wherein the directing step further comprises delivering the portion of water from the header into the end of the at least one heat exchange conduit in the interior or exterior column of heat exchange conduits. 